Semi-conductor components, for instance corresponding integrated (analog and/or digital) computer circuits, semi-conductor memory components, for instance functional memory components (PLAs, PALs, etc.) and table memory components (e.g. ROMs or RAMs, in particular SRAMs and DRAMs) are subjected to extensive testing during the manufacturing process.
For the simultaneous combined manufacture of numerous (generally identical) semi-conductor components, a so-called wafer (i.e. a thin disk of monocrystalline silicon) is used. The wafer is appropriately treated (for instance subjected in succession to numerous coating, exposure, etching, diffusion and implantation process steps, etc.), and then for instance sliced up (or scored and snapped off), so that the individual components become available.
During the manufacture of semi-conductor components (for instance DRAMs (Dynamic Random Access Memories and/or dynamic read-write memories), in particular of DDR-DRAMs (Double Data Rate-DRAMs and/or DRAMs with double data rate)) semi-completed components (still on the wafer) can be subjected—even before the above process steps required for the wafer have been completed (i.e. even while the semi-conductor components are still in a semi-complete state)—to appropriate test processes at one or more test stations (for instance so-called kerf measurements at the wafer scoring frame) with the aid of one or more test apparatuses.
After completion (i.e. after completion of all the above wafer processing steps) the semi-conductor components are subjected to further test procedures at one or more (further) test stations. For instance, completed components—still present on the wafer—can be appropriately tested with the aid of corresponding (additional) test equipment (“slice tests”).
After the wafers have been sliced up (and/or scored and snapped off) the—individually available components—are next each loaded into a so-called carrier (i.e. a suitable mounting), whereupon the semi-conductor components—loaded into the carrier—can be subjected to one or several (further) test procedures corresponding with other test stations.
In the same way, one or more further tests (at corresponding test stations and with the use of appropriate additional test equipment) can be performed, for instance after the semi-conductor components have been mounted onto the corresponding semi-conductor component housing, and/or for instance after the semi-conductor component housing (together with the semi-conductor components mounted onto it in each case) has been mounted (for so-called module tests) into a corresponding electronic module.
In testing the semi-conductor components, (for instance with the above slice tests, module tests, etc.) so-called “DC tests” and/or for instance so-called “AC tests” may in each case be applied.
For a DC test for instance, a particular voltage (or current)—in particular one remaining at a particular fixed level—can be applied to the appropriate connection of a semi-conductor component to be tested, whereafter the level of the—resulting—current (and/or voltage) can be measured by the test apparatus, in particular to ascertain whether these currents (and/or voltages) fall within certain predetermined desired critical limits.
During an AC test in contrast, voltages (or currents)—at varying levels—can for instance be applied to the appropriate connections of a semi-conductor component by the test apparatus as test signals, in particular as appropriate test sample signals with the aid of which appropriate function tests can be performed on each semi-conductor component.
With the help of the above test procedures, defective semi-conductor components can be identified and removed (or to a certain extent even repaired).
In so doing it must be ensured—especially when using high-frequency (AC) test signals—that the signals emitted by each test apparatus and applied to each semi-conductor component connection by means of a corresponding test line, are not (too severely) corrupted, for instance by reflections or noise resulting from signal distortions etc. caused by contact inductivity; in other words, that the quality of the test signals satisfy the requirements in each case.
Testing the signal quality of the test signal present at each semi-conductor component connection is a difficult process.
When the test signal, emitted by each test apparatus for assessing signal quality and present at each semi-conductor component connection, is for instance fed to an appropriate signal measuring apparatus by means of an additional external test line (or for instance fed back to the test apparatus), the electrical characteristics of the semi-conductor component connection are changed by the—additional—test line (and the apparatus connected to it), whereby the test signal to be measured and/or assessed is distorted.